The problem for SOU is that it is in golfing terms playing with just one club in it's bag - FlyBe. That club has recently been repaired, but nobody knows how it's going to perform going ahead, and whether it's going to perform best as a driver or a putter! It won't any longer be all things to all men.
This means that some airports will likely catch a cold; others may prosper. The winners, I suspect will be particular MAN, and possibly LHR. The losers BHX, and I fear SOU. That's not to say they'll withdraw from either, but that their presence will be somewhat diminished. Some airports may lose them altogether. The next six months may be crucial.
What the loser airports will have to do is find some new players to fill the holes, and aside of Loganair I'm struggling to see where they will come from, especially with a potential no deal Brexit closing the door to EU operators operating domestically in UK.